problem with no$gba in MMZ2

[chrono kid]

Ive already gotten the linking to work but I have an interesting hurdle in megaman zero 2, theres a link option that allows the trading of special powers and abit of combat, but when I boot up the game ,with carts in both gba mind you, the second gba has no save data, and that is neccecary to do the multiplayer. Also, I have played past the first mission on the second gba and saved, restarted the game, same issues.

finally, zelda the four swords DOESN'T have this problem but aparantly uses player 2's saved data.

any help for me?

ps. WHAT is multiboot and whys it need a bios file?